The Firing Cycle as a Dependent Variable

Each phosphor composition has its own unique, but required, firing cycle. Note that we consolidate firing time and firing temperature together, because they are inter-dependent. First of all, we choose a temperature that is above the minimum temperature required for the solid state reaction. In many cases, this is a matter of experience, but this minimum is easily obtained from DTA and TGA data. A temperature at least 200 C. above this minimum is generally required. What we find is that there are certain combinations of firing time and temperature which produce the best results in terms of quality of phosphor so-produced. 

An example for the phosphor, YNb04 Eu is shown in 6.5.14., given on the next page. Tills phosphor was produced by the solid state reaction  

The measured responses (a measure of relative energy efficiency) are shown in the diagram as slopes, where the topology varies in the z direction. The x direction is the time variable and the y direction is the temperature variable. What we have is a ridge (denoted by the straight line in the middle) where the firing cycle effects, i.e.- the combination of T and t, are linear. 

From this diagram, we can choose a proper firing cycle for either of these phosphors, providing that we use the oxalates of the rare earths as raw materials. 

As an example of how the solid state reaction proceeds to form the 

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